Re: [RFC 1/2] cfg80211/mac80211: add regulatory_hint_found_beacon() to make help world roaming

[Johannes Berg <johannes@sipsolutions.net>]

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On Mon, 2009-02-02 at 21:01 -0800, Luis R. Rodriguez wrote:
> This adds some initial intelligence to help world roaming. When we
> are world roaming we have no idea what country we are in yet and
> because of this our regulatory domain will be pretty restrictive.
> Country information elements help and we have code to handle that already,
> however, not many APs enable country IEs. We can help the situation
> by adding checks on ours scans for beacons from APs, if we are world roaming
> and an AP beacon is found on a channel we will make the bet that we can
> also beacon and do active scanning -- when not on radar channels.
> 
> Since this goes in as part of cfg80211 all devices present will benefit
> from any device's found beacons, this includes new devices connected or
> when you disconnect and reconnect the same device.
> 
> Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>

NACK. If we do this _after_ cfg80211 scanning it becomes so much
simpler.

> ---
>  include/net/wireless.h |   20 +++++
>  net/mac80211/mlme.c    |   35 +++++++++
>  net/wireless/reg.c     |  181 +++++++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 235 insertions(+), 1 deletions(-)
> 
> diff --git a/include/net/wireless.h b/include/net/wireless.h
> index a42c156..74b0352 100644
> --- a/include/net/wireless.h
> +++ b/include/net/wireless.h
> @@ -69,6 +69,9 @@ enum ieee80211_channel_flags {
>   * @band: band this channel belongs to.
>   * @max_antenna_gain: maximum antenna gain in dBi
>   * @max_power: maximum transmission power (in dBm)
> + * @beacon_found: helper to regulatory code to indicate when a beacon
> + * 	has been found on this channel. Use regulatory_hint_found_beacon()
> + *	to enable this, this is is useful only on 5 GHz band.
>   * @orig_mag: internal use
>   * @orig_mpwr: internal use
>   */
> @@ -80,6 +83,7 @@ struct ieee80211_channel {
>  	u32 flags;
>  	int max_antenna_gain;
>  	int max_power;
> +	bool beacon_found;
>  	u32 orig_flags;
>  	int orig_mag, orig_mpwr;
>  };
> @@ -414,6 +418,22 @@ extern void regulatory_hint_11d(struct wiphy *wiphy,
>  				u8 country_ie_len);
>  
>  /**
> + * regulatory_hint_found_beacon - hints a beacon was found on a channel
> + * @wiphy: the wireless device where the beacon was found on
> + * @beacon_chan: the channel on which the beacon was found on
> + *
> + * This informs the wireless core that a beacon from an AP was found on
> + * the channel provided. This allows the wireless core to make educated
> + * guesses on regulatory to help with world roaming. This is only used for
> + * world roaming -- when we do not know our current location. This is
> + * only useful on channels 12, 13 and 14 on the 2 GHz band as all other
> + * channels are already enabled by the world regulatory domain; and on
> + * non-radar 5 GHz channels.
> + */
> +extern int regulatory_hint_found_beacon(struct wiphy *wiphy,
> +					struct ieee80211_channel *beacon_chan);
> +
> +/**
>   * wiphy_apply_custom_regulatory - apply a custom driver regulatory domain
>   * @wiphy: the wireless device we want to process the regulatory domain on
>   * @regd: the custom regulatory domain to use for this wiphy
> diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
> index 9d51e27..45905dc 100644
> --- a/net/mac80211/mlme.c
> +++ b/net/mac80211/mlme.c
> @@ -2717,6 +2717,7 @@ void ieee80211_mlme_notify_scan_completed(struct ieee80211_local *local)
>  {
>  	struct ieee80211_sub_if_data *sdata = local->scan_sdata;
>  	struct ieee80211_if_sta *ifsta;
> +	struct ieee80211_bss *bss;
>  
>  	if (sdata && sdata->vif.type == NL80211_IFTYPE_ADHOC) {
>  		ifsta = &sdata->u.sta;
> @@ -2731,6 +2732,40 @@ void ieee80211_mlme_notify_scan_completed(struct ieee80211_local *local)
>  	list_for_each_entry_rcu(sdata, &local->interfaces, list)
>  		ieee80211_restart_sta_timer(sdata);
>  	rcu_read_unlock();
> +
> +	/* Send off hints to the wireless core about beacons found */
> +	spin_lock_bh(&local->bss_lock);
> +
> +	sdata = local->scan_sdata;
> +
> +	list_for_each_entry(bss, &local->bss_list, list) {
> +		struct wiphy *wiphy;
> +		struct ieee80211_supported_band *sband;
> +		struct ieee80211_channel *chan;
> +		unsigned int i;
> +
> +		if (!(bss->capability & WLAN_CAPABILITY_ESS))
> +			continue;
> +
> +		wiphy = sdata->local->hw.wiphy;
> +
> +		if (WARN_ON(!wiphy->bands[bss->band]))
> +			continue;
> +
> +		sband = wiphy->bands[bss->band];
> +
> +		for (i = 0; i < sband->n_channels; i++) {
> +			chan = &sband->channels[i];
> +
> +			if (chan->center_freq != bss->freq)
> +				continue;
> +			if (regulatory_hint_found_beacon(wiphy, chan))
> +				goto unlock_and_exit;
> +		}
> +	}
> +
> +unlock_and_exit:
> +	spin_unlock_bh(&local->bss_lock);
>  }
>  
>  void ieee80211_dynamic_ps_disable_work(struct work_struct *work)
> diff --git a/net/wireless/reg.c b/net/wireless/reg.c
> index 2323644..656cad7 100644
> --- a/net/wireless/reg.c
> +++ b/net/wireless/reg.c
> @@ -54,6 +54,18 @@ static u32 supported_bandwidths[] = {
>  	MHZ_TO_KHZ(20),
>  };
>  
> +/*
> + * This list is used to help regulatory when devices are still
> + * world roaming.
> + */
> +static LIST_HEAD(reg_beacon_list);
> +
> +/* Used to help world roaming, used on found beacons */
> +struct reg_beacon {
> +	struct list_head list;
> +	struct ieee80211_channel chan;
> +};
> +
>  /* Central wireless core regulatory domains, we only need two,
>   * the current one and a world regulatory domain in case we have no
>   * information to give us an alpha2 */
> @@ -758,6 +770,141 @@ static u32 map_regdom_flags(u32 rd_flags)
>  	return channel_flags;
>  }
>  
> +static void handle_reg_beacon(struct wiphy *wiphy,
> +			       unsigned int chan_idx,
> +			       struct reg_beacon *reg_beacon)
> +{
> +#ifdef CONFIG_CFG80211_REG_DEBUG
> +#define REG_DEBUG_BEACON_FLAG(desc) \
> +	printk(KERN_DEBUG "cfg80211: Enabling " desc " on " \
> +		"frequency: %d MHz (Ch %d) on %s\n", \
> +		reg_beacon->chan.center_freq, \
> +		ieee80211_frequency_to_channel(reg_beacon->chan.center_freq), \
> +		wiphy_name(wiphy));
> +#else
> +#define REG_DEBUG_BEACON_FLAG(desc) do {} while (0)
> +#endif
> +	struct ieee80211_supported_band *sband;
> +	struct ieee80211_channel *chan;
> +
> +	sband = wiphy->bands[reg_beacon->chan.band];
> +	chan = &sband->channels[chan_idx];
> +
> +	if (likely(chan->center_freq != reg_beacon->chan.center_freq))
> +		return;
> +
> +	if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN) {
> +		chan->flags &= ~IEEE80211_CHAN_PASSIVE_SCAN;
> +		REG_DEBUG_BEACON_FLAG("active scanning");
> +	}
> +
> +	if (chan->flags & IEEE80211_CHAN_NO_IBSS) {
> +		chan->flags &= ~IEEE80211_CHAN_NO_IBSS;
> +		REG_DEBUG_BEACON_FLAG("beaconing");
> +	}
> +
> +	chan->beacon_found = true;
> +#undef REG_DEBUG_BEACON_FLAG
> +}
> +
> +/*
> + * Called when a scan on a wiphy finds a beacon on
> + * new channel
> + */
> +static void wiphy_update_new_beacon(struct wiphy *wiphy,
> +				     struct reg_beacon *reg_beacon)
> +{
> +	unsigned int i;
> +	struct ieee80211_supported_band *sband;
> +
> +	if (!wiphy->bands[reg_beacon->chan.band])
> +		return;
> +
> +	sband = wiphy->bands[reg_beacon->chan.band];
> +
> +	for (i = 0; i < sband->n_channels; i++)
> +		handle_reg_beacon(wiphy, i, reg_beacon);
> +}
> +
> +/*
> + * Called upon reg changes or a new wiphy is added
> + */
> +static void wiphy_update_beacon_reg(struct wiphy *wiphy)
> +{
> +	unsigned int i;
> +	struct ieee80211_supported_band *sband;
> +	struct reg_beacon *reg_beacon;
> +
> +	if (list_empty(&reg_beacon_list))
> +		return;
> +
> +	list_for_each_entry(reg_beacon, &reg_beacon_list, list) {
> +		if (!wiphy->bands[reg_beacon->chan.band])
> +			continue;
> +		sband = wiphy->bands[reg_beacon->chan.band];
> +		for (i = 0; i < sband->n_channels; i++)
> +			handle_reg_beacon(wiphy, i, reg_beacon);
> +	}
> +}
> +
> +static bool freq_is_chan_12_13_14(u16 freq)
> +{
> +	if (freq == ieee80211_channel_to_frequency(12) ||
> +	    freq == ieee80211_channel_to_frequency(13) ||
> +	    freq == ieee80211_channel_to_frequency(14))
> +		return true;
> +	return false;
> +}
> +
> +int regulatory_hint_found_beacon(struct wiphy *wiphy,
> +				 struct ieee80211_channel *beacon_chan)
> +{
> +	struct cfg80211_registered_device *drv;
> +	struct reg_beacon *reg_beacon, *beacon;
> +
> +	if (beacon_chan->beacon_found ||
> +	    (beacon_chan->flags & IEEE80211_CHAN_RADAR) ||
> +	    (beacon_chan->band == IEEE80211_BAND_2GHZ &&
> +	     !freq_is_chan_12_13_14(beacon_chan->center_freq)))
> +		return 0;
> +
> +	reg_beacon = kzalloc(sizeof(struct reg_beacon), GFP_KERNEL);
> +	if (!reg_beacon)
> +		return -ENOMEM;
> +
> +#ifdef CONFIG_CFG80211_REG_DEBUG
> +	printk(KERN_DEBUG "cfg80211: Found new beacon on "
> +		"frequency: %d MHz (Ch %d) on %s\n",
> +		beacon_chan->center_freq,
> +		ieee80211_frequency_to_channel(beacon_chan->center_freq),
> +		wiphy_name(wiphy));
> +#endif
> +	memcpy(&reg_beacon->chan, beacon_chan,
> +		sizeof(struct ieee80211_channel));
> +
> +	mutex_lock(&cfg80211_drv_mutex);
> +
> +	list_for_each_entry(drv, &cfg80211_drv_list, list)
> +		wiphy_update_new_beacon(&drv->wiphy, reg_beacon);
> +
> +	/*
> +	 * If this happens it means our beacon_found flag isn't
> +	 * working as intended.
> +	 */
> +	list_for_each_entry(beacon, &reg_beacon_list, list) {
> +		if (WARN_ON(beacon->chan.center_freq ==
> +		    reg_beacon->chan.center_freq))
> +			goto unlock;
> +	}
> +
> +	list_add_tail(&reg_beacon->list, &reg_beacon_list);
> +
> +unlock:
> +	mutex_unlock(&cfg80211_drv_mutex);
> +	return 0;
> +}
> +EXPORT_SYMBOL(regulatory_hint_found_beacon);
> +
>  static int freq_reg_info_regd(struct wiphy *wiphy,
>  			      u32 center_freq,
>  			      u32 *bandwidth,
> @@ -938,16 +1085,38 @@ static void update_all_wiphy_regulatory(enum reg_set_by setby)
>  		wiphy_update_regulatory(&drv->wiphy, setby);
>  }
>  
> +static bool reg_is_world_roaming(struct wiphy *wiphy)
> +{
> +	if (is_world_regdom(cfg80211_regdomain->alpha2) ||
> +	    (wiphy->regd && is_world_regdom(wiphy->regd->alpha2)))
> +		return true;
> +	if (last_request->initiator != REGDOM_SET_BY_COUNTRY_IE &&
> +	    wiphy->custom_regulatory)
> +		return true;
> +	return false;
> +}
> +
> +/* Reap the advantages of previously found beacons */
> +static void reg_process_beacons(struct wiphy *wiphy)
> +{
> +	if (!reg_is_world_roaming(wiphy))
> +		return;
> +	wiphy_update_beacon_reg(wiphy);
> +}
> +
>  void wiphy_update_regulatory(struct wiphy *wiphy, enum reg_set_by setby)
>  {
>  	enum ieee80211_band band;
>  
>  	if (ignore_reg_update(wiphy, setby))
> -		return;
> +		goto out;
>  	for (band = 0; band < IEEE80211_NUM_BANDS; band++) {
>  		if (wiphy->bands[band])
>  			handle_band(wiphy, band);
>  	}
> +
> +out:
> +	reg_process_beacons(wiphy);
>  	if (wiphy->reg_notifier)
>  		wiphy->reg_notifier(wiphy, last_request);
>  }
> @@ -1633,6 +1802,8 @@ int regulatory_init(void)
>  
>  void regulatory_exit(void)
>  {
> +	struct reg_beacon *reg_beacon, *reg_tmp;
> +
>  	mutex_lock(&cfg80211_drv_mutex);
>  
>  	reset_regdomains();
> @@ -1644,5 +1815,13 @@ void regulatory_exit(void)
>  
>  	platform_device_unregister(reg_pdev);
>  
> +	if (!list_empty(&reg_beacon_list)) {
> +		list_for_each_entry_safe(reg_beacon, reg_tmp,
> +		  &reg_beacon_list, list) {
> +			list_del(&reg_beacon->list);
> +			kfree(reg_beacon);
> +		}
> +	}
> +
>  	mutex_unlock(&cfg80211_drv_mutex);
>  }

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